232
CHAPTER 6
Growth and study of gel grown crystals of Bismuth Tri-
Sulphide Bi2S3
Paper published:-
1. “Growth and study of gel grown crystals of Bismuth Tri-Sulphide
[Bi2 S3] ” T. K. Patil and K. B. Saraf
Der Chemica sinica journal of Pelagia library volume 1(3)
December 2010 Page numbers 48 to 55 [ISSN-0976-8505].
2. “Magnetic and Electric properties of Intrinsic semiconductor Bismuth Tri-
Sulphide [Bi2 S3] grown by Gel method” T. K. Patil and K. B. Saraf
Journal of Nano Electron Physics volume 3 (2011) No 1 page
numbers 610 to 619 [PACS numbers: 68.37 HK, 75.40Cx]
233
CHAPTER 6
Growth and study of gel grown crystals of Bismuth Tri-
Sulphide Bi2S3
6.1 Introduction.................................................................... 234
6.2 Crystal growth................................................................ 235
6.2.1 Apparatus used............................................ 235
6.2.2 Chemicals used............................................ 236
6.2.3 Experimental procedure.............................. 236
6.3 Results and discussion...................................................... 237
6.4 Observations..................................................................... 238
6.5 Effect of various parameters............................................ 240
6.5.1 Effect of gel density......................................... 240
6.5.2 Effect of pH of the gel...................................... 242
6.5.3 Effect of gel aging............................................ 243
6.5.4 Effect of concentration of reactants................ 245
6.5.5 Concentration programming........................... 246
6.6 Characterization................................................................. 246
6.6.1 Introduction..................................................... 246
6.6.2 X-ray diffractometry (XRD)............................... 247
6.6.3 FT-IR analysis... ................................................. 250
6.6.4 Thermal studies................................................. 252
6.6.4.1 Thermo Gravimetric Analysis (TGA)........ 253
6.6.4.2 Differential Thermal Analysis (DTA)........ 256
6.6.4.3 Differential Thermo Gravimetry (DTG)... 257
6.6.4.4 Differential Scanning Calorimetry (DSC).. 258
6.6.5 Chemical analysis................................................ 260
6.6.5.1 Estimation of strontium............................ 260
6.6.5.2 Estimation of iodine.................................. 263 6.6.6 Energy Dispersive Analysis by X-rays (ED AX)…. 267
6.6.7 Scanning Electron Microscopy........................... 268
6.6.8 Electrical conductivity ....................................... 270 6.6.9 Magnetic Susceptibility………………………………………………. 272
6.7 Conclusions....................................................................... 274
References................................................................................. 276
234
CHAPTER 6
Growth and study of gel grown crystals of Bismuth Tri-
Sulphide Bi2S3
6.1 Introduction:
The growth of crystals in gels was recorded in 1913 when Liesegang, Bradford
and Holmes studied the formation of 'Liesegang rings' (Liesegang 1914, Bradford
1926, Holmes 1926). Afterwards, mechanism of growth has been discussed
extensively by many co-workers (Henisch et.al.1965, Henisch and Hanoka 1965,
O’Connor and Armington 1967, Dennis and Henisch 1967, Halberstadt and
Henisch 1968, Robert and Lefaucheux 1988, Andreazza et al.1988, Shitole and
Saraf 2001, Shitole and Saraf 2002). Their work accelerated the mechanism of
growth and characterization of crystals of gel grown.
A variety of crystals required for the purpose of research and application
can be grown in silica gels. The gel medium prevents turbulence and being
chemically inert, it provides a three-dimensional crucible which permits the
reagents to diffuse at a desirable controlled rate. Its softness and uniform nature
of constraining forces that it exerts upon the growing crystals encourages orderly
growth (Patel and Venkateswara Rao 1978; Shitole and Saraf 2001).
The growth of crystals in gel at an ambient temperature, which are
sparingly soluble in water, is a fascinating alternative to the techniques involving
high temperature and expensive equipments (Sangawal and Patel 1974). During
the last few years, successful application of gel growth technique has been
demonstrated by the preparation of crystals of alkaline earth metal iodate
(Joshi and Trivedi 1983). The gel growth technique appeared quite attractive for
growing crystals of such compounds on account of its unique advantages in terms of
crystals produced and the simplicity of process (Armington and O’Connor 1968;
Blank and Brenner 1969; Blank et al 1969, Randive et al 1969; Blank 1973).
235
Crystals of Iodate exhibit nonlinear optical properties (Kurtz and Perry 1968;
Morosin et al 1973) and piezoelectric properties (Bach and Kuppers 1978).
Nonlinear optical phenomenon have found a wide variety of applications in many
areas of modern science, technology and engineering. The nonlinear devices find
large applications in optical communication, image processing, and wave-guide
coupling.
In recent years, few attempts have been made to study growth and
characterization of Sulphide crystals in general and Bismuth Tri-Sulphide
crystals in particular. However, there are no reports in the literature on the
growth of these crystals by gel method. Hence, the growth of Bismuth Tri-
Sulphide crystals by gel technique by single diffusion method is under taken.
The present chapter reviews several aspects regarding the growth
procedure of Bismuth Tri-Sulphide crystals, optimum growth conditions and the
kinetics i.e. influence of different growth parameters to obtain optimization
conditions for the growth of these crystals. This chapter also predicts the results
obtained from the different techniques used for the characterization of gel
grown crystals of Bismuth Tri-Sulphide.
6.2 Crystal growth:
The growth of Bismuth Tri-Sulphide crystals in gel media is based on the
diffusion method. In the present work Single diffusion method is used for the growth
of Bismuth Tri-Sulphide crystals in gel media.
6.2.1 Apparatus used:-
• Borosil glass test tubes
• Magnetic stirrer
• Digital pocket-sized pH meter (HANNA instrument)
• Burettes and pipettes
• Beakers
236
• Specific gravity bottle
6.2.2 Chemicals used:
• Commercial grade sodium Meta silicate (Na2SiO3 5H2O)
• Acetic acid, AR grade, Loba chemicals (CH3COOH)
• Bismuth chloride, AR grade, Loba chemicals (BiCl3)
• H2S gas water solution.
6.2.3 Experimental procedure:
The chemical reaction method is used to grow the Bismuth Tri-Sulphide
crystals. This method involves growing of crystals by allowing the reaction of
solution of soluble salt Bismuth chloride and H2S gas water solution by diffusion
through a gel with subsequent nucleation and the crystal growth, which continues
due to the gradual precipitation of insoluble product.
In the present work, single diffusion method was used. In actual
procedure, 5cc, 2N acetic acid was taken in a small beaker, to which sodium
Meta silicate solution of density 1.04 gm/cc was added drop by drop with
constant stirring by using magnetic stirrer, till pH of the solution reaches a
value of 4.40. A digital pocket sized pH meter of HANNA instruments is used for
this purpose. Continuous stirring process avoids excessive ion concentration
which otherwise causes premature local gelling and makes the final medium
inhomogeneous and turbid. To this mixture, 5cc of Bismuth Chloride (one of the
reactants) was added with constant stirring. The pH of the mixture was
maintained at 4.4. Numbers of experiments were carried out in order to secure
appropriate range of pH values which in turn gives a good gel allowing to
growing good quality crystals.
The chemical reactions inside the gel can be expressed as
2XCl3 + 3Y2S → X2S3 + 6YCl
Where X=Bi and Y= H
237
6.3 Results and discussions:
Crystals in Circular rings of little mm size were obtained. Study of kinetics
of growth parameters reveals some interesting information. These types of
Circular rings of crystals were reported by Liesegang and have been explained
previously (Bolotov 1968). The result of this is a rounded crystal, but at first the
basal planes (the plane of the sheet of the paper) are bent at random. These
serves as the base for two-dimensional nuclei, which grow and fill up the recesses on
the outer surface, thus giving crystal a circular shape.
Higher density gel sets more rapidly. It decreases nucleation density.
Increased density reduces diffusivity of ions which in turn reduces growth rate
(Andreazza et al. 1988). Lower density gel takes long time to set and can be
easily fractured. Increase in aging of gel reduces number of nucleation centers and
growth rate. The reason may be the formation of additional cross-linkages between
siloxane chains with increasing gel age, resulting in a gradually reducing cell size
(Halberstadt 1969). This, in turn, reduces nucleation centers, since many nuclei
find themselves in cells of very small size, where further growth is not possible.
Insufficient gel aging leads to the formation of fragile gel and often breaks at the
time of addition of supernatant. The effect of pH on growth rate was studied by
changing pH without a change of gel composition and concentration of reactants.
With pH values less than 4, gel takes longer time to set and is unstable. There is
no considerable effect on the quality of crystal. Higher pH value gel sets early,
becomes turbid, and the size of crystal becomes smaller. As the pH increases, the
gel structure changes from distinctly box-like network to a structure of loosely
bound platelets, which appear to lack cross-linkages and the cellular nature
becomes less distinct. Less concentration of reactants does not yield any crystals
at all. High concentration yields crystals of smaller size with increased nucleation
centers. Reported concentration of reactants when used yields smaller
238
spherulites near the gel interface with more number of nuclei. This may be due
to high diffusion gradient near the gel interface. As the distance from the gel
interface increases, number of nuclei reduces and size of spherulite increases
due to smaller concentration gradient. Slow diffusion should lead to better
nuclei, which because of their higher energy content should be less likely to
reach their critical size. So the pH value 4.40 is well for growth of good quality
crystals. The optimum growth conditions for various parameters were found and
are reported in Table 6.1. Different parameters such as gel density, gel setting
time, gel aging time, concentrations of reactants, pH of gel etc have the
considerable effect on the growth rate.
Table 6.1: Optimum conditions for growth of Bismuth Tri-Sulphide crystals
Conditions Bismuth Tri-Sulphide
Density of sodium meta silicate solution 1.04 g/cm3
Amount of 2N acetic acid 5ml
pH of the gel 4.40
Temperature Room temperature Concentration of BiCl3 0.5 M
Concentration of H2S gas water solution. - - - -
Gel setting time 13 days
Gel aging time 72 hours
Period of growth 31 days
6.4 Observations:-
On the quality of the crystals, various concentrations of reactants
have different effects. Figure 6.1 shows Bismuth Tri-Sulphide crystals
incorporated in the gel. Spherulites of Bismuth Tri-Sulphide crystals grown for
these different concentrations of BiCl3 ranging from 0.1 M to 1 M are shown in
the figures 6.1. It is observed that as the concentration of Bismuth Tri-Sulphide
increased from 0.1M to 1M, the size and the quality of the spherulites also
goes on increasing. The crystals so formed are spherical in shape, opaque and
well isolated. Figure 6.2 shows few spherical
graph paper with their scaling.
Fig. 6.1 Crystals of Bismuth
Fig 6.2 Few Crystals of Bismuth
239
Figure 6.2 shows few spherical Bismuth Tri-Sulphide crystals
graph paper with their scaling.
Fig. 6.1 Crystals of Bismuth -Trisulphide inside the Test-tube.
Fig 6.2 Few Crystals of Bismuth-Trisulphide on graph paper.
Sulphide crystals on a
240
6.5 Effect of various parameters on crystal growth:-
Study of kinetics of growth parameters reveals some interesting
information. Effect of concentration of reactants, gel density, pH of the gel, gel
aging and concentration programming etc. was studied and is presented in this
section with respect to the results obtained.
6.5.1 Effect of gel density:-
The gels of different densities were obtained by mixing sodium Meta
silicate solutions of specific gravity 1.03 to 1.06 with 2N acetic acid, keeping pH
value constant. It was observed that as the gel density increases, transparency of
the gel decreases. Gels with higher densities taken less gel setting time compared
to the gels with lower densities. It may be noted that Well-defined and
transparent single crystals were obtained with sodium Meta silicate density
1.04 gm/cc. On the other hand, gels with densities below 1.04 gm/cc taken
longer time to set and still gels were not stable. Density of 1.03 gm/cc was the
lower practical limit.
It is observed that the nucleation density decreases with increase in gel
density. Table 6.2 shows the effect of density on number of nuclei formed. It
has been graphically shown in Fig. 6.3. A greater gel density implies smaller pore
size and poor communication among the pores and thus decreasing the
nucleation density. Bechhold et al showed that diffusion coefficient becomes
distinctly smaller as gel densities increase. There is no evidence that the diffusion
constant of small atoms and ions is greatly influenced by the silica gel density as long
as the density is low. Thus, the diffusion constants are not greatly influenced by
the presence of dilute gel. In the present work, gel density of the value 1.04
gm/cc is the optimum condition for the growth of good quality crystals.
241
Table 6.2: Effect of gel density on nucleation density [pH = 4.4, feed solution H2S
water gas solution]
Test
tube
No.
Acetic
acid
IN (cc)
BiCl3
incorporated
in gel l.OM (cc)
Density of
gel (gm/cc)
Number of
nuclei formed
Observations
1 5 5 1.02 58 High nucleation density,
very small sphere shaped
crystals 2 5 5 1.03 52 Small sphere shaped
crystals in ring form
3 5 5 1.04 44 Small gray coloured
spheres near gel
interface, in ring form
4 5 5 1.05 30 Small gray coloured in
ring form
5 5 5 1.06 24 Small gray coloured in
ring form
6 5 5 1.07 18 Small gray coloured in
ring form
010203040506070
1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08
Density of gel (gm/cc)
Num
ber
of n
ucle
i fo
rmed
Series1
Figure 6.3 Plot of gel density against nucleation density
242
6.5.2 Effect of pH of gel:
By changing the pH of gel without changing gel composition and concentration
of reactants, the effect of pH on growth rate was studied
Table 6.3: Effect of pH on gel [Aging period = 72 hrs, feed solution H2S water gas
solution]
Test
tube
No.
Acetic
acid
2N
(cc)
BiCl3
incorporated
in gel l.OM
(cc)
Sodium
meta
silicate
1.04
(gm/cc)
pH
of
Mixture
Gel
Setting
Time
(hours)
Observations
1 5 5 17.5 2.0 - Gel is not set
2
5
5
17.8
2.5 - Gel is not set
3
5
5
18.2
3.0 - Gel set in 18 days
but still unstable
4
5
5
18.7
3.5 360 Cream coloured
spherulites
5
5
5
19.0
4.2 336 Spherulites less in
number
6
5
5
19.5
4.4 312 Small spheres less in
number
7
5
5
20.1
4.5 264 Small spheres
8
5
5
21.6
5.0 180 Small spheres
9 5 5 21.1 5.5 120 Very small crystals
10
5
5
21.6
6.0 96 Very small spherical
crystals
11 5 5 22.5 6.5 48 small spheres with
very low
nucleation density
The pH value of gel was varied from 2 to 6. It was observed that gel of pH
less than 4.0 took longer time to set and was unstable. There was no
considerable effect of change in pH on the quality of crystals. Higher pH value
gel sets early, becomes turbid, and the size of crystal-becomes smaller. As pH
increases, the gel structure changes from distinctly boxlike network to a structure
243
of loosely bound platelets, which appears to lack cross-linkages and the cellular
nature becomes less distinct. Number of nuclei also decreases and the crystals
are not well defined, due to improper formation of cells at high pH values. Table
6.3 shows the effect of different pH values on the quality of crystals. Fig. 6.4
illustrates the graph of setting time versus pH of mixture. In the present work, pH
value of 4.4 is the optimum condition for the growth of good quality crystals.
0
50
100
150
200
250
300
350
400
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0
pH of Mixture
Gel
Set
ting
Tim
e (h
ours
)
Figure 6.4 Plot of pH against gel setting time
6.5.3 Effect of gel aging:
Gel aging plays an effective role on the growth of crystals as reported by
Henisch et al. To investigate the effect of aging on gels, gels of same pH and density
were allowed to age for various periods before adding the feed solution. It was
found that the nucleation density decreases as the aging increases. Aging of gel
reduces number of nucleation centers and growth rate. The reason may be the
formation additional cross-linkages between siloxane chains with increasing gel
age, resulting in a gradually diminishing cell size. This in turn reduces nucleation
centers, since many nuclei find themselves in cells of very small size, where further
growth is not possible. Insufficient gel aging leads to the formation of fragile gel
and it often breaks at the time of addition of supernatant. The effect of gel aging
244
time on the number and the quality of crystals is as shown in the table 6.4. Figure
6.5 shows the graph of aging time in hours against the number of crystals.
Table 6.4: Effect of gel aging time (pH = 4.4, feed solution H2S water gas solution]
Test
tube
No.
Acetic
acid 2N
(cc)
BiCl3
incorporated
in gel l.OM (cc)
Sodium
meta
silicate 1.04
gm/cc)
Aging
time
(hours)
Number
Of
crystals
Observations
1 5 5 18 36 100 High nucleation density,
very small crystals
2 5 5 18 48 92 Still High nucleation
centre’s with same size as
above 3 5 5 18 72 80 High nucleation, density,
medium size as above
4 5 5 18 96 60 Small crystals near gel
interface, tinny at the
middle of the gel column.
5 5 5 18 120 42 Nucleation density
reduces, small and
spherical
6 5 5 18 144 35 Less in number, smaller in
size
7 5 5 18 168 24 Less in number, smaller in
size
Figure 6.5 Plot of gel aging time against nucleation density
In the present work, aging of 72 hours was found suitable because it makes the
gel neither dry or brittle nor fragile. The aim of reduction in nucleation centers can
0
20
40
60
80
100
120
0 50 100 150 200
Aging time (hours)
Num
ber
of c
ryst
als
245
also be achieved. Hence aging period of 72 hours is the optimum condition for
the growth of good quality crystals.
6.5.4 Effect of concentration of reactants-:
The effects of concentration of feed solutions can be investigated by preparing the
gel of the same pH and density. Feed solution of BiCl3 of different concentrations
and H2S gas water solution as a supernant are used. [H2S gas passed for fix time 6 to
8 hours ] Table 6.5 summarizes the effects of concentration of reactants on habit,
quality, and size of single crystals.
Table 6.5: Effect concentration of reactants on habit, quality and size of Bi2S3
crystals
Concentration of
reactant in gel
Concentration of
reactant above gel
Habit
Quality
BiCl3
0.1 M; 5 ml
H2S gas water
solution
Smaller spherulites, less
in number
Gray coloured,
opaque
BiCl3
0.2 M; 5 ml
H2S gas water
solution
Smaller spherulites Gray coloured,
opaque
BiCl3
0.3 M; 5 ml
H2S gas water
solution
Spherulites of smaller
size more in number
Gray coloured,
opaque
BiCl3
0.5 M; 5 ml
H2S gas water
solution
Spheres more in number Gray coloured,
opaque
BiCl3
0.6 M; 5 ml
H2S gas water
solution
Spheres of medium size
more in number
Whitish,
Opaque
BiCl3
1.0 M; 5 ml
H2S gas water
solution
Larger spherulites, well
isolated
Opaque, Gray
coloured
Gray
Experiments were carried out by changing the solution of BiCl3 of different
molarities ranging from 0.1M to l.OM was incorporated in gel and preparation i.e.
pass H2S gas in double distilled water for 7,8,10,11 and 12 hours was put over the
set gels. It had been observed that the use of H2S gas water solution and BiCl3
yields better quality crystals, in terms of size and shape. Therefore, after getting
246
the optimized conditions, all experiments were carried out by incorporating' 5cc,
0.5 M BiCl3 solution in gel and H2S gas water solution as Supernatant.
6.5.5 Concentration programming:-
Once the optimum growth conditions for concentration of reactants are established,
Single diffusion experiments of concentration programming were carried out in
order to observe the nucleation control phenomenon. Good H2S gas water
solution [passed H2S gas for 6 to 8 hours] was prepared. After setting and sufficient
aging of gel, 20 ml of H2S gas water solution was slowly poured over the acidified
gel. This feed solution was replaced by another equal volume feed solution in next
48 hours. The strength of feed solution was increased in quantity 20 to 25ml. It was
found that the nuclei previously formed, began to grow to their optimum size.
6.6 Characterization of gel grown crystals of mercuric iodate
6.6.1 Introduction:-
There are no perfect crystals in reality and all crystals grown by any
technique contain some defects, impurities and in homogeneities. Most of the
physical properties are sensitive to the deviation from ideality. Hence,
characterization of the grown crystals is essential. The need for high quality
crystals is increasing and only systematic characterization makes it possible for
the crystal grower to optimize the growth parameters in order to obtain better
crystals. The assessment of the physical and chemical perfection of materials is
generally known as characterization.
Experimental techniques used to characterize Bismuth Tri-Sulphide crystals
are already discussed in the chapter 3 in detail. This chapter deals with the results,
which are obtained from the different techniques used for the characterization of
gel grown single crystals of Bismuth Tri-Sulphide. The results of these
observations have been described and discussed below.
247
6.6.2 X-ray diffractometry (XRD):-
Every crystalline substance has a unique X-ray powder diffraction pattern
from which a characteristic set of interplaner spacings (d) and relative intensities
can be derived. Materials are identified from these values in conjunction with
the JCPDS powder diffraction file. X-ray is today a widely used tool to determine
crystal structures.
X-ray diffractogram of gel grown crystals of Bismuth trisulphide Bi2S3 was
recorded at NCL PUNE with the help of “miniflex goniometer (1.5405 A˚) X-Ray
diffractogram in the range of 0˚ to 70˚ was obtained and the scanning speed
was kept 2˚ per minute also chart kept 2 cm per minute.
Copper target and nickel filter were used from the powder diffraction data of
Bismuth trisulphide shows Eighteen different peaks and corresponding d
values &[ h,k,l] values was computed by using computer program POWD [an
interactive powder diffraction data interpretation and indexing program]The
recorded X-Ray diffractogram is as shown in fig 6.6.
Fig 6.6 X- Ray diffractogram of Bismuth-Trisulphide
248
The Powder diffraction data for gel grown crystals is as shown in table –6.6.
The observed values are very well match with calculated values from computer
program and also match with JCPDS card No - 06 - 0333 of Bi2S3 observed
peaks in diffractogram shows Bismuth-trisulphide crystals passes Rhombus or
Orthorhombic structure is as shown in table 6.7
Table 6.6 Powder diffraction data for gel grown crystals
Peak No. 2 Theata FWHM d-value Intensity I/Io
1 3.940 0.188 22.4066 357 60
2 12.060 0.447 7.3323 326 55
3 24.200 0.447 3.6746 134 23
4 25.900 0.424 3.4371 424 71
5 32.600 0.424 2.7444 348 59
6 33.540 0.424 2.6696 600 100
7 34.940 0.235 2.5658 44 8
8 36.560 0.400 2.4557 113 19
9 40.940 0.376 2.2025 192 32
10 46.720 0.424 1.9423 187 32
11 48.440 0.376 1.8776 56 10
12 49.820 0.471 1.8287 198 33
13 53.240 0.29 1.7190 42 7
14 54.240 0.447 1.6897 200 34
15 55.120 0.471 1.6648 138 23
16 58.700 0.471 1.5715 285 48
17 60.560 0.212 1.5276 96 17
18 68.160 0.353 1.3746 88 15
249
Table 6.7 Calculated and observed values of d and h, k, l.
In Rhombus crystal structure the length of unit cells are different .but the three
axis are perpendicular to each other i.e. a ≠ b ≠ c & α = γ = β=900 as shown in
table 6.8
Table 6.8 Calculated unit cell parameters
Peak
No
Intensity 2 Theta in degree 2˚ FWHM Indices
h k l
d spacing value(A˚)
Observed calculated Observed Calculated
1 357 3.940 3.848 0.188 3 0 2 22.4066 22.4078
2 326 12.060 12.266 0.447 2 3 0 7.3323 7.3318
3 134 24.200 24.040 0.447 1 1 1 3.6746 3.6756
4 424 25.900 25.910 0.424 3 1 0 3.4371 3.4300
5 348 32.600 32.594 0.424 3 0 1 2.7444 2.7404
6 600 33.540 33.499 0.424 3 1 1 2.6696 2.6490
7 44 34.940 34.798 0.235 2 4 0 2.5658 2.5600
8 113 36.560 36.528 0.400 2 3 1 2.4557 2.4560
9 192 40.940 40.985 0.376 1 4 1 2.2025 2.2045
10 187 46.720 46.732 0.424 4 3 1 1.9423 1.9450
11 56 48.440 48.508 0.376 0 6 0 1.8776 1.8740
12 198 49.820 49.818 0.471 6 1 0 1.8287 1.8340
13 42 53.240 53.276 0.29 0 6 1 1.7190 1.7130
14 200 54.240 54.301 0.447 1 6 1 1.6897 1.6820
15 138 55.120 55.098 0.471 6 1 1 1.6648 1.6650
16 285 58.700 58.697 0.471 2 4 2 1.5715 1.5720
17 96 60.560 60.564 0.212 7 2 0 1.5276 1.5230
18 88 68.160 68.158 0.353 1 1 6 1.3746 1.3700
Sr. No. Lattice parameters Bismuth trisulphide Bi2S3
1 System Rhombus or orthorhombic
2 a 11.136 A˚
3 b 11.256 A˚
4 c 3.968 A˚
5 α 90.18˚
6 β 90.42˚
7 γ 90.36˚
8 v 496.84 ( A˚)3
250
Result and discussion
1) In rhombus or orthorhombic crystal structure the no. of different lattice is
four and lattice symbol denoted by P, C, I and F cells.
2) Grain size determination of Bismuth trisulphide from XRD spectra. As seen
from the XRD pattern each peak has got a finite width the grain size is
determined by measuring the width of the line with highest intensity peak. The
grain size is 0.3415nm. The grain size can be calculated by using formula.
Grain size D = 0.9 λ/ β Cos θ Where λ= wavelength = 1.54056 A˚
Β = Is full width of half maxima (FWHM) in radian=0.424radian
D = grain size of crystal
θ = 16.77 degree Highest peak intensity at 600
D=0.9 λ/ β Cos θ = 0.9 x 1.54056 / 0.424 x Cos [16.77]
= 1.38645/ 0.424 x 0.9574 = 1.38645 / 0.4059
= 3.3457 A˚ = 0.3415 nm
6.6.3 Fourier Transform Infrared Spectroscopy (FTIR)
An FTIR spectrum of Bismuth Trisulphide (Bi2S3 of 1M and 0.5 M) crystals was
recorded using SIMADZU Spectrometer at department of chemistry, university
of Poona.
The FTIR Spectrum for a particular chemical compound is unique
characteristics alone. Reflecting as it does the geometry. Band strength and
atomic masses of the substance. Therefore an important use of FTIR is the
Identification of unknown functional group present in the chemical
compounds. The FTIR Spectra of Bismuth trisulphide (Bi2S3) is as shown in fig
6.7 the spectrum is scanned in region 4000 to 500 cm-1
using SHIMADZU
spectrometer at department of chemistry in University of Pune. The result of
FTIR spectra of Bismuth trisulphide crystals with observed band and their
assignment are shown in table (6.9)
251
Fig 6.7 FTIR Spectra of Bismuth Trisulphide (0.5M).
Table 6.9 FTIR spectra analysis of Bismuth Trisulphide (Bi2S3) crystals
Sr. No. IR Peaks (Spectrum) cm-1
Intensity Assignment
1 3662.94to3603.15 Broad band,
strong
O-H stretching
2 3603.15 to 3064.99 Strong and broad O-H stretching
3 2860 Normal and weak C-H stretching with
high energy
4 1712.85 strong, sharp C=O stretching
5 966.37and960.58 Strong, sharp O-H out of plane
stretching (olefinic)
6 806.27and800.49 Strong, sharp C-H bond
out of plane
stretching
7 752.26to704.04 Weak and broad C-O or C-C stretching
out of plane vibration
8 462.93 to 428.21 strong and sharp Bismuth metal to
Sulpher
A few of the prominent vibration modes are empirically assigned here
the bands around 3662.94 to 3603.15cm-1
attributed to asymmetric and
252
symmetric O-H stretching of water. The O-H stretching freq appeared
between3603.15to 3064.99 cm-1
is probably due to stretching vibration of
Hydroxyl group-H bonded may be due to Si-OH or O-H stretching of acetic acid.
The weak band appearing at 2860 cm-1
can be attributed to C-H stretching of
Alkyl group. It may be due to the present of impurity of Bismuth acetate.
The strong &sharp band appearing at 1712.85 cm-1
can be attributed
stretching vibration of Acetyl carbonyl group [ ] with C=O
stretching. The frequency Band appearing at 966.37to960.58 cm-1
can be
attributed to bending freq. of O-H group out of plane. (Olefinic) The freq band
appearing at 806.27&800.49 cm-1
can be attributed to bending freq. of C-H
group out of plane.
The freq. band appearing at 752.26 to704.04 cm-1
can be attributed to
stretching freq of C-O or C-C stretching out of plane. The freq band appearing
at 462.93 to 428.21 can be attributed to metal Bismuth to Sulpher bond in
same plane. The Crystal structure of Bismuth Trisulphide is as shown below.
Fig 6.8 Crystal structure of Bismuth trisulphide
6.6.4 Thermal Analysis or Thermal studies
The Thermograms were obtained with the help of Diamond TGA/DTA
thermal analyzer available at National Chemical Laboratory (NCL), Pune 7.
Recrystallization alumina sample holders were used and the heating rate was
300 C/min. the weight of sample was 08.785 mg for TGA/DTA/DTG studies and
253
03.600 mg for DSC.
6.6.4.1 Thermal Gravimetric Analysis (TGA)
It was confirmed that the thermal decomposition of Bismuth Tri-
Sulphide passes through an intermediate 2[Bi2S3.H2O] which is unstable and
immediately decomposes to Bi2O3. It has a one stage course until Bi2O3 is
obtained an intermediate 2[Bi2S3.H2O] is obtained in this process analogously
as in the thermal decomposition of the alkaline earth Sulphides. However
unlike 2[Bi2S3.H2O] immediately after it is obtained begins to decomposition to
Bi2O3 Di-Hydrus Bismuth Tri-Sulphide decomposes at high temperature.
According to following reactions
2 [Bi2S3.H2O]+ 9O2 37.271 to 102.271 [2 H2O + 2SO2 ]
Step I heating
5 [Bi (IO3)3 2H2+ 102.271 to 947.271 [4SO2 ]
Step II heating
[2Bi2 O3 ]
Stable Residue + [2Bi2 O3 ] Stable
Fig 6.9 TGA curve of Bismuth Tri-Sulphide
254
Table 6.10 TGA data of Bismuth Tri-Sulphide
Stages temperature (o C) Observed
weight loss %
Calculated
weight loss %
Probable loss
of molecule
I 37.271 to 102.271 13.543 % 12.130 % 2 H2O + 2SO2
II 102.271 to 947.271 14.984 % 18.934 % 4SO2
Total weight loss 28.527 % 31.064 %
Residue
Stable [2Bi2 O3 ]
71.472 %
68.930 %
2 Bi2 O3
Observed Weight Loss:-
1. 37.271 to 102.271
99.748 – 86.205 = 13.543 %
2. 102.271 to 947.271
86.205 – 71.221 = 14.984 %
Calculated Weight Loss
2 [Bi2S3.H2O]+ 9O2 [ 2 H2O + 2SO2 ]
2 x 514 +18X2+ 18X16 = 18 x 2 + 2 x32+4X16
= 1028 +36+ 288 = 36 + 64 = 64
= 1352 = 164 x 100/1352 = 12.130 %
5 [Bi (IO3)3 2H2 O] [4SO2 ]
5 x 734 + 180 = 4 x 32 + 16 x 8
= 3670 + 180 = 128 + 128 = 256
= 3850 = 256 x 100/1352 = 18.934%
5 [Bi (IO3)3 2H2O]
Residue [ 2 Bi2 O3 ]
2Bi2 O3 = 4 x 209 + 6 x 16
255
= 836 + 96 = 932
= 932 x 100/1352
=68.930
The TGA curve for Bismuth Tri-Sulphide gel grown crystals is as shown in
fig 6.9 The TGA data collected from this curve and the theoretical values as
calculated from molecular formula using the reaction are listed in table 6.10
TGA data and curve of Bismuth Tri-Sulphide showed clearly two stages of
decomposition. TGA curve did not show an appreciable weight changes in the
temperature 00 C to 37.271
0 C indicating that the crystals of Bismuth Tri-
Sulphide are thermally stable in this range. The crystals becomes thermally
unstable from 37.2710
C.
1. The first stage of decomposition occurs in the temperature range
37.271 to 102.271 0C in which observe weight loss of 13.543 % agree with
calculated weight loss 12.130 %. This weight loss is attributed to loss of [2 H2O
+ 2SO2 ] and decomposition is in continuous manner.
2. The second stage of decomposition occurs in the temperature range
102.271 to 947.2710C in which observed weight loss of 14.984 % nearly agree
with calculated weight loss 18.934 %. Here observed weight loss appear to be
less as compared with calculated can be attributed to incomplete
decomposition of Bi2S3, The further weight loss expected may be seen at still
higher temperature up to which we could not proceed our experiment. This
weight loss is attributed to loss of [4SO2 ] and decomposition is in continuous
manner.
The remaining product finally turns into residue Bi2O3 (Bismuth Oxide) is
conformed at 947.271OC the observed residue weight is 71.472 %. This is
nearly agreement with calculated residual weight 68.930%.This confirms
presents of Bismuth in grown crystals.
256
6.6.4.2 Differential Thermal Analysis (DTA)
The DTA curve for Bismuth Tri-Sulphide gel grown crystal is as shown in
the fig 6.10 and DTA data collected from this curve is tabulated in table 6.11
Fig 6.10 DTA curve of Bismuth Tri-Sulphide
Table 6.11 DTA data of Bismuth Tri-Sulphide
Sr.
No
Peak
recorded
Nature Peak
height
µV
On set Area
(m J)
∆H
(J/gm)
1 82.28 0
c Endothermic 16.625 37.57 0
c 328.65 56.954
2 302.57 0c Endothermic 0.547 197.66
0 c 206.40 24.117
In DTA curve we can observe two endothermic peaks at 82.28 0
c and 302.57 0
c. However exothermic peak was not noticed in the DTA graph.
1. The endothermic peak at 82.28 0c is due to the decomposition of
Bismuth Tri-Sulphide losing [2H2O +2SO2 ] molecules means in the first stage
of decomposition peak at 82.28 0
c is attributed to the loss of 2 water and 2SO2
molecules. This endothermic peak observed in the DTA curve corresponds to
the weight loss of 2 water and 2SO2 molecules in TGA curve.
257
2. The second endothermic peak at 302.57 0c is due to the
decomposition of compound and this peak in the second stage of
decomposition is attributed to the loss of 4SO2 molecules. This endothermic
peak observed in the DTA curve corresponds to the weight loss of 4SO2
molecules in the DTA curve.
Above 947.271 0c the reaction proceeds once finally residue Bi2O3
remains up to end of the analysis.
6.6.4.3 Differential Thermal Gravimetric (DTG) The DTG curve for
Bismuth Tri-Sulphide gel grown crystal is as shown in the fig 6.11 and DTG data
collected from this curve is tabulated in table 6.12
Table 6.12 DTG data of Bismuth Tri-Sulphide
Fig 6.11 DTG curve of Bismuth Tri-Sulphide
Sr. No Peak On set Inflection point
1 73.33 0c 46.66
0 c 63.73
0 c
2 183.33 0c 102.271
0 c 121.33
0 c
258
1. The exothermic peak at 73.33 0c is due to the decomposition of
Bismuth Tri-Sulphide losing 2 water and 2SO2 molecules in the first stage of
decomposition. This exothermic peak observed in the DTG curve indicates that
the reaction starts at 46.66 0c and the inflection occurs at 63.73
0c. The peak
observed in DTG curve corresponds to the weight loss of 2 water and 2SO2
molecules in TGA curve.
2. The endothermic peak at 183.33 0c is due to the decomposition of
compound and this peak in second stage of decomposition is attributed to the
loss of 4SO2 molecules. This endothermic peak observed in the DTG curve
indicates that the reaction starts at 102.271 0c and the inflection occurs at
121.33 0c. The peak observation in DTG curve corresponds to the weight loss of
4SO2 molecules in TGA curve.
Above 947.271 0c the reaction proceeds once finally stable residue Bi2O3
remains up to end of the analysis.
6.6.4.4 Differential Scanning Calorimetery (DSC)
The DSC curve for Bismuth Tri-Sulphide gel grown crystal is as shown in
the fig 6.12 and DSC data collected from this curve is tabulated in table 6.13
Fig 6.12 DSC curve of Bismuth Tri-Sulphide
259
Table 6.13 DSC data of Bismuth Tri-Sulphide
Sample Weight of
sample
Change in Enthalpy
(∆H)
Transition
temperature
Bismuth
Tri-Sulphide
[ Bi2S3 ]
3.600 mg
0.0775 KJ/mole 66.86 0c
0.0149 KJ/mole 237.73 0c
There are two stages of DSC curves under study as follows
Stage I
1. The initiation temperature is 34.22 0c and equilibrium temperature is 118.33
0c at 34.22
0c (initiation temperature) initiation of phase change starts and is
completed at peak endo-down temperature of 66.86 0c transition temperature
[peak height is 1.2673 mw]. The temperature at which the sample and the
reference come to the thermal equilibrium by thermal diffusion appears to be
at 118.33 0c.
2. Area under the curve is 279.126 mJ.
3. Heat of transition ∆H i.e. enthalpy change of transition is 77.5350 J/g
which is 0.0775 KJ/mole since molecular weight is 1.000 g/mole
∆H tran = ∆HF of phase transformation is also 0.0775 KJ/mole where
∆HF is enthalpy change of new phase formation or it is called heat of phase
formation.
Stage II
1. The initiation temperature is 177.00 0c and equilibrium temperature is
343.89 0c at 177.00
0 c (initiation temperature) peak height is 0.0887 mW
initiation of phase change starts and is completed at peak endo-down
temperature of 273.73 0c (transition temperature). The temperature at which
the sample and the reference come to the thermal equilibrium by thermal
260
diffusion appears to be at 343.89 0c
2). Area under the curve is 53.717 mJ.
3). Heat of transition ∆H i.e. enthalpy change of transition is 14.9213 J/g
which is 0.0149 KJ/mole since molecular weight is 1.000 g/mole
∆H tran = ∆HF i.e. heat of phase transformation is also 0.0149 KJ/mole
where ∆HF is enthalpy change of new phase formation or it is called heat of
phase formation.
6.6.5 Chemical Analysis
6.6.5.1 Gravimetric Chemical Analyses of Bi2S3 Bismuth Trisulphide
Estimate of Bismuth (Bi) From Bi2S3
Bismuth is estimeted gravimetrically using dil HCl by Homogneous
precipetation. Accurately wighed 0.1gm of sample in powder form was
dissolved in small quantity of double distilled water. Few drops of HCl
(Hydrochloric Acid) were added to disolve the powder completely. A volume
of solution was accuratly made equal to 100 ml by adding double distill
water to it. Sodium Acetate and 2N Acitic acid (CH3COOH) were added to
this solution so as to make the pH between 4.40 to 4.60.
This solution was then heated for 40-45 minutes in water bath. The solution
was filtered through Dr. Watts filter paper and washed several times with
warm distilled water. There was remaining residue of BiCl3 on the filter paper.
The residue was cooled and dried in oven. Weight of BiCl3 residue obtained
was 0.1187gm.
Weight of sample = 0.1 gm
Weight of filter paper + precipitate = 1.1587 gm
Weight of filter paper = 1.04 gm
Weight of the residue = 0.1187 gm
1.Theoretical percentage of Bismuth (Bi)Theoretically Bi2S3 having molecular
261
weight = 514.20 gm/mole. The amount of Bismuth is 208.98 gm/mole
for Bi2, 208.98 X 2 = 417.96 %
% of Bismuth = 417.96x100/514.20
= 41796/514.20 = 81.28 %
Thus theoretically in 100 gm of Bi2S3 there is 81.28% of Bismuth.
2. Practical Percentage of Bismuth (Bi):- Practically in BiCl3 having
molecular weight 315.17gm/mole. The amount of Bismuth in BiCl3 is 208.98
gm/mole.
Bi2S3 + 6HCl => 2BiCl3 + 3H2S
Therefore In 0.1187 gm of BiCl3 residue.
Amount of Bismuth (Bi) = 208.98 X 0.1187/315.17
= 24.8227/315.17
=0.07876 gm
Thus amount of Bismuth in Bismuth Chloride is practically 0.07876 gm. Since in
0.1 gm of sample powder there is 0.07876 gm of Bismuth
% of Bi =0.07876x100/0.1
=7.876/0.1 =78.76%
Thus practically in 0.1 gm of Bi2S3 sample there is 78.76 % Bismuth.
Estimation of Sulpher:-
Accurately weighed 0.1 gm of sample in powder form was dissolved in
small quantity of double distilled water. Few drops of Nitric Acid were added
while heating to dissolve the powder completely. Few ml of dilute silver Nitrate
(AgNO3) was then added. The mixture was heated in water bath until the
precipitate was obtained. It was allowed to stand for some time. Precipitate
was then filtered through Dr. Watt’s filter paper and washed several times with
warm distilled water. The residue obtained in this procedure was weighed
after heating it in oven along with the fitter paper.
262
• Weight of sample = 0.1 gm
• Weight of filter paper with precipitate = 1.1703 gm
• Weight of filter paper = 1.04 gm
• Weight of residue = 0.1303 gm
Theoretical percentage of Sulpher (S) :-
Theoretically in Bi2S3 having molecular weight 514.20 gm/mole the amount of
Sulpher (S) is 32.06 gm/mole for S3 32.06x3 = 96.18 gm/mole
Percentage of Sulpher (S) = 96.18x100/514.20
= 9618/514.20 = 18.70%
Thus theoretically in 100 gm of Bi2S3 there is 18.70% Sulpher (S)
Practical percentage of Sulpher (S) :-
Practically in Ag2S having molecular weight 247.86 gm/mole.
For 3Ag2S = 247.86 x 3 = 743.58 gm/mole and amount of Sulpher is 32.06
gm/mole. For S3 = 32.06x3=96.18 gm/mole.
Bi2S3+6AgNO3 2Bi (NO3)3+3Ag2S
% of Sulpher (S) = 96.18x0.1303/743.58
= 12.5367/743.58
= 0.01686 gm
Thus amount of Sulpher in 3Ag2S is practically = 0.01686 gm since in 0.1gm
of sample powder of there is 0.01686 gm of Sulpher (S).
Percentage of Sulpher (S) = 0.01686x100/0.1
= 1.686/0.1 = 16.86%
Thus practically in 0.1 gm of Bi2S3 sample there is 16.86 % of Sulpher (S)
Thus result of chemical analysis is as shown in the table 6.14 from table
we observed that the experimental values of Bismuth (Bi) and Sulpher (S)
are in good agreement with the theoretical ones. (Values)
263
Table 6.14 Result of chemical Analysis
Element Theoretical
values (%)
Practical
values (%)
Bismuth 81.28 78.76
Sulpher 18.70 16.86
99.98 95.62
6.6.5.2 Volumetric / Titrimetric Analysis of Bi2S3 Bismuth trisulphide
Estimation / Determination of Bismuth from Bi2S3 :-
Bismuth trisulphide Bi2S3 solution was quantitatively (volumetrically)
estimated with standard EDTA solution Take 0.5 gm Bismuth trisulphide
crystals dissolved in small quantity of double distilled water. Add few drops
of concentrated HCl to dissolved sample powder completely. The volume of
solution becomes 250 ml by adding double distilled water. Then 10 ml
solution pipetted in titration flask Add Hexamine buffer till the PH is 4.40
Add 2 or 3 drops of Xylenol orange as a indicator the solution become red
then titrate it with standard EDTA solution until the color changes from red
to yellow.
Reading of titration = 7.65 ml
Practically 1 mole EDTA = 1mole of Bi+++
In 1000 ml, 1mole EDTA Solution contain = 208.98 gm of Bismuth hence
0.01 mole EDTA solution, Contain
% of Bismuth = 208.98x0.01x7.65/1000
= 2.0898x7.65/1000
= 15.9869/1000
= 0.01598
As 10 ml diluted solution = 0.01598 gm of Bismuth.
250 ml diluted solution contain
264
=0.01598x250/10
= 3.9967/10
=0.3996
0.5 gm of Bismuth trisulphide = 0.3996
For 100 gm of Bismuth trisulphide
= 0.3996x100/0.5
=39.96/0.5
= 79.93%
Thus practically in Bi2S3 there is 79.93% of Bismuth.
Theoretically in Bismuth trisulphide the Bismuth = 81.28%
i. e. Bi2S3 have mole wt = 514.20 gm/mole amount of Bismuth = 208.98
gm/mole hence for Bi2= 208.98x2 = 417.96 gm
% of Bismuth =417.96x100/514.20
= 41796/514.20
= 81.20 %
Thus theoretically in Bi2S3 there is 81.20% of Bismuth.
Estimation / Determination of Sulpher from Bi2S3 :-
Bismuth trisulphide Bi2S3 solution was quantitatively i.e. Volumetrically /
Titrimetically Estimated with standard 0.05M Iodine solution.
Take 0.5 gm Bismuth trisulphide crystals dissolved in small quantity of
double distilled water. Add few drops concentrated HCl to dissolve the sample
powder completely. The volume of solution becomes 250 ml by Adding double
distilled water. Then 10ml solution pipetted in titration flask Add hexamine
buffer till the pH is 4.40 Add 2 or 3 drops of starch as an indicator. The solution
becomes Blue. Then titrate it with 0.05M standard Iodine solution until the
color changes from Blue colorless. Reading of titration = 3.80 ml
265
Theoretically in Bismuth trisulphide having Mole wt = 524.20 gm
Amount of Sulpher = 32.06
For S3 = 32.06x3 = 96.18
For Sulpher = 96.18x100/514.20 =9618/514.20
= 18.70 %
Theoretically in 100 gm of Bi2S3 there is 18.70 % of Sulpher.
Practically 1 mole of Iodine = 1 mole of Sulpher S-
In 1000 ml contain, 1 ml of Iodine 96.18 gm Sulpher
Hence 0.01 Iodine Contain =96.18x0.01x3.80/1000
= 3.6548/1000 = 0.003652
As 10 ml diluted solution = 0.003652 gm of Sulpher.
Hence 250 ml diluted solution contain =0.003652x250/10
= 0.9131/10
= 0.09131
0.5 gm of Bismuth Tri-Sulphide = 0.0931.
Hence 100 gm of Bismuth trisulphide = 0.09131x100/0.5
= 9.13/0.5
= 18.26%
Practically 0.5 gm of Bi2S3 sample there is 18.26% of Sulpher. From table we
observed that Experimental values by volumetric analysis match with
theoretical values.
Table6.15 Result of volumetric analysis for Bi2S3
Sr.
No.
Element Theoretical
value (%)
Practical
Value ( %)
1 Bismuth 81.28 79.93
2 Sulpher 18.70 18.26
99.98 97.19
266
6.6.5.3 Specific gravity of Bismuth Trisulphide Bi2S3
Specific gravity --specific gravity may be defined as the ratio of mass of
substance to the mass of an equal volume of other substance taken as
standard. Example for Bi2S3 water may be standard
Take 0.257 gm of Bismuth Trisulphide Bi2S3 powder dissolve it with small
quantity of double distilled water. Add few drops of HCl to dissolve powder
completely. A volume of solution is accurately made 50 ml. this is solution of
0.01 m.
As where M= molecular weight
C = concentration
Q= quantity
= 514.20 x 0.01x 50/1000
= 0.257 gm
Take 25 ml solution of Bi2S3 to determine specific gravity
[25 ml sp. Gravity Bottle is used]
* Weight of empty sp gravity bottle w1 = 13.80 gm
* Weight of sp gravity bottle + water W2 = 44.40 gm
* Weight of bottle + liquid [solution of Bi2S3] W3 = 230.29gm
* Weight of liquid solution of Bi(Io3)3
W4= W3 - W1 W4 = 216.49 gm
* Weight of water W5 = W2 - W1 W5 = 30.60 gm
* Density of water W6 = 0.9979 gm/m
Sp gravity of Liquid Bi2S3
=
W 4/W5 = 216.49x0.9979/30.60
267
= 241.035/30.60 = 7.07 gm/cm3
Sp gravity of Bi2S3 Practically is 7.07 gm/cm3 is well match with Theoretical
value 7.39 gm/cm3
6.6.6 EDAX: - Energy Dispersive Analysis by X rays (EDAX).
Elemental Dispersive Analysis by X rays (EDAX) is used for the quantitative
analysis. In the present work elemental analysis of gel grown Bismuth Tri
Sulphide, crystals was carried out at the NCL National Chemical Laboratory
Pune fig 6.13 shows EDAX spectrum of Bismuth Tri Sulphide Table 6.16 shows
the values of elemental content of the crystals as measured by the EDAX
technique and the theoretical calculations from molecular formula. From the
table it is clear that values of (wt %) and (At %) of Bi2S3 in grown crystals
measured EDAX are close to with the estimated values calculated from
molecular formula.
,
1 2 3 4 5 6 7 8 9 10keV
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
cps/eV
Bi O Si S
S
Fig 6.13 Energy Dispersive Spectrum of Bi2S3
268
Table 6.16 Calculation of elemental analysis of gel grown Bismuth Tri
Sulphide
97.4 3 99.98
6.6.7 SEM: - Scanning Electron Microscopy of Bi2S3
In present work Scanning Electron Microscopy of powdered sample of
gel grown Bismuth Tri Sulphide crystals was carried at NCL (National Chemical
Laboratory) Pune and the successive photographs were taken at the
magnification of 0.5, 1.50, 2.00, 5.00 & 10.00 KX all the photographs were
taken at common width 9 mm and EHT magnification 20 KV. And represented
as Fig (6.14.1) to (6.14.6) shows SEM images of the powdered sample of
Bismuth Tri Sulphide. Fig (6.14.1) shows the part of crystals of Bismuth Tri
Sulphide. It is observed that the face is neither dull nor very bright but it has
some bright region at the left half of the fig. whole the surface is covered with
figs of different shapes & size. Some of the figs are approximately seen to be
triangular & pentagonal.
The edges triangle & pentagonal are clearly seen in some cases but in
some cases they are not so cleared. In general the shape is clearly seen, these
figs are randomly oriented on the whole surface In fig 6.14.1 a small region
labeled as small (a), at 0.5 KX is shown as (A) in fig 6.14.2. At 1.50 KX the
magnification all three fig in A region are pentagonal on minute observation fig
(X) in region (A) is perfectly pentagonal with well defined boundaries while the
remaining two figs does not have well defined start boundaries.
Element Content measured by
EDAX
Content as calculated from
molecular formula Bi2S3
Wt % At % Wt % At %
Bismuth 79.87 % 73.88 81.28 % 74.76
Sulphur 17.56 % 24.57 18.70 % 25.23
269
Fig 6.14.1 Region I
Fig 6.14.2 Region II
Fig 6.14.3 Region III
Fig 6.14.4 Region IV
Fig 6.14.5
Fig 6.14.6
Fig (6.14.1) to (6.14.6) shows SEM images of the powdered sample of
Bismuth Tri Sulphide.
. In fig 6.14.3 shows different region with higher magnification the edges
of figs have in general marked boundaries because of higher magnification
attachment of micro crystals are individual grains is clearly seen. The region
270
marked by (B) in fig 6.14.3 shows attachment of many micro crystals. If we
compare region (B), (C) & (D) on fig 6.14.3 region B has more attachment of
micro crystals than region (C), also by comparing region (C) & (D) region (C) has
maximum micro crystals than (D) means we compare the attachment of micro
crystals in region (B), (C) & (D) simultaneously we may conclude that it is due
to different growth conditions on the same face. The growth rate in the region
(B) is higher as compare to region (C) & the growth rate is controlled in the
region (D).
This supports the fact that the growth conditions are varying on
different parts of same face of the crystals. The same thing of growth
conditions are observed in region (E) of fig 6.14.4. In region (E) one defined
hexagon marked by (F) is seen to be in regular shape of hexagon having
marked boundary and size of equal length i.e. from fig 6.14.4 shows controlled
growth condition as attachment of micro crystals in different part of fig is less.
Whereas attachment of micro crystals is more in different part of fig 6.14.5 i.e.
Region shown in fig 6.14.4 have controlled condition as compare to fig 6.14.5.
If fig 6.14.6 is observed it indicates well defined some pentagon with no
attachment of micro crystals i.e. it confirms the controlled growth conditions.
6.6.8 MAGNETIC SUCCEPTIBILITY: -
In present work Magnetic Susceptibility of powdered sample of gel grown
Bismuth Tri-Sulphide crystals was carried out at Department of Physical
Science, N.M.U. Jalgaon.
Observations:-
A. Weight of empty holder + Holder Assembly (test tube) without magnetic
field= 4.595 gm
B. Weight of empty holder + Holder Assembly (test tube) + sample powder without
magnetic field = 4.615 gm
271
Observation Table: - 6.17 MAGNETIC SUCCEPTIBILITY of Bi2S3
Sr.No Current
in A
Magnetic
Field (H)
Gauss
Weight of
sample in
gm
Difference
in wt m
χχχχ m x 10-6
cm3
mole-1
1 0 0 4.615 ---- 0
2 0.2 172 4.617 - 0.002 - 0.05385
3 0.4 366 4.617 - 0.002 - 0.01189
4 0.6 524 4.617 - 0.002 - 0.005802
5 0.8 703 4.616 - 0.001 - 0.001611
6 1.0 868 4.616 - 0.001 - 0.001057
7 1.2 1044 4.614 + 0.001 + 0.0007309
8 1.4 1187 4.614 + 0.001 0.0005654
9 1.6 1354 4.614 + 0.001 0.0004345
10 1.8 1543 4.613 + 0.002 0.0006692
11 2.0 1720 4.613 + 0.002 0.0003885
C. Weight of sample powder M= b – a = 4.615 – 4.595 = 0.020 gm
• m = Change in weight (m) of sample powder with magnetic field
= 0.002 gm
• L = Height of sample powder in test tube = 1.1cm
• ρ = Density of specimen = 7.39 g/cm3
• H = Applied magnetic field = 366 gauss (for 0.4 A current)
• M= Weight of specimen examine = 0.020 gm
• g = Acceleration due to gravity = 980 cm/sec2
Formula: - The magnetic susceptibility (χχχχ ) of Bismuth Tri Sulphide (Bi2S3)
powder is given by relation. χχχχ = 2mgLρ/MH2
= 2 x (- 0.002) x 980 x 1.1 x 7.39 / 0.020 x (366)2
272
χχχχ = - 0.01189 = -118 x 10-6
cm3
mole-1
Fig 6.15. Graph of Magnetic Field (H) Gauss V/s χχχχ m x 10-6
cm3
mole-1
6.6.9 ELECTRICAL CONDUCTIVITY of BISMUTH TRI SULPHIDE Bi2S3
In present work Electrical Conductivity of powdered sample of gel grown
Bismuth Tri-Sulphide crystals was carried at Department of Chemical Science,
N.M.U. Jalgaon.
OBSERVATIONS :- 1) Height /thickness of pallet = 0.536 cm
OBSERVATIONS :- 2) Diameter of the pallet = 0.942 cm
OBSERVATIONS :- 3) Radius of pallet = r = 0.471 cm =d/2
OBSERVATIONS :- 4) Voltage = 0.50 mv (constant)
K = l/RA K= l/Rπr2
(since A=πr2 )
l = 0.536 cm = 5.36 x 10 -4
m
r = 0.471 cm = 4.71 x 10 -4
m)
K = 5.36 x 10 -4
/ R x 3.142 x (4.71 x 10 -4
)2
K = 5.36 x 10 -4
/ R x 3.142 x (4.71)2 x 10
-8
K = 5.36 / R x 3.142 x (4.71)2 x 10
-4
K = 5.36 x 104 / R x 3.142 x22.18 K = 5.36 x 10
4 / R x 69.702
K = 0.07690 x 104/
R K =7.6901 x 102/
R K =769.01 /R
K = 415.27 mho/cm
273
Table: - 6.18 ELECTRICAL CONDUCTIVITY of BISMUTH TRI SULPHIDE Bi2S3
Sr.
No
Temp
T o k
1x10 -4
/T
Current in
A I x 10 -4
Resistance
R in ΩΩΩΩ R x 10 -4
Conductivity in
mho/cm Kx 10 -4
Log K
1 423 23.64 0.28 = 2.8 x 10 -4
01.7857 430.64 2.63411437
2 418 23.92 0.28 = 2.8 x 10 -4
01.7857 430.64 2.63411437
3 413 24.21 0.27 = 2.7 x 10 -4
01.8518 415.27 2.61833056
4 408 24.50 0.26 = 2.6 x 10 -4
01.9230 399.9 2.6019514
5 403 24.81 0.23 = 2.3 x 10 -4
02.1739 353.74 2.54868417
6 398 25.12 0.23 = 2.3 x 10 -4
02.1739 353.74 2.54868417
7 393 25.44 0.20 = 2.0 x 10 -4
02.5000 307.6 2.48798633
8 388 25.77 0.19 = 1.9 x 10 -4
02.6315 292.33 2.46587339
9 383 26.10 0.19 = 1.9 x 10 -4
02.6315 292.33 2.46587339
10 378 26.75 0.18 = 1.8 x 10 -4
02.7777 276.85 2.44224453
11 373 26.80 0.16 = 2.1 x 10 -4
03.1250 246.08 2.39107632
12 368 27.17 0.16 = 1.6 x 10 -4
03.1250 246.08 2.39107632
13 363 27.54 0.15 = 1.5 x 10 -4
03.3333 230.7 2.36304759
14 358 27.93 0.14 = 1.4 x 10 -4
03.5714 215.32 2.33308437
15 353 28.32 0.13 = 1.3 x 10 -4
03.8461 199.94 2.30089969
16 348 28.73 0.12 = 1.2 x 10 -4
04.1616 184.78 2.26665496
17 343 29.15 0.12 = 1.2 x 10 -4
04.1616 184.78 2.26665496
18 338 29.58 0.11 = 1.1 x 10 -4
04.5454 169.18 2.22834902
19 333 30.03 0.09 = 0.9 x 10 -4
05.5555 138.42 2.14119884
20 328 30.48 0.09 = 0.9 x 10 -4
05.5555 138.42 2.14119884
21 323 30.95 0.08 = 0.8 x 10 -4
06.2500 123.04 2.09004632
22 318 31.44 0.07 = 0.7 x 10 -4
07.1428 107.66 2.03205438
23 313 31.94 0.07 = 0.7x 10 -4
07.1428 107.66 2.03205438
24 308 32.46 0.06 = 0.6 x 10 -4
08.3333 92.28 1.96510759
25 305 32.78 0.04 = 0.4 x 10 -4
12.5000 61.52 1.78901633
Calculations :- 1) I = 0.28 m A = 2.8 x 10 -4
A
V = 0.5 mV = 5 x 10 -4
V
R = V/I = 5 x10 -4
/ 2.8 x 10 -4
= 1.7857 Ω
K = 769.01 / R = 769.01
/ 1.7857
K = 4.3064 x 100
K = 430.64 mho/cm
2) I = 0.27 m A = 2.7 x 10 -4
A
V = 0.5 mV = 5 x10 -4
V
R = V/I = 5 x10 -4
/ 2.7 x 10 -4
= 1.8518 Ω
274
K = 769.01 / R = 769.01
/ 1.8518
K = 4.1527 x 100 K = 415.27 mho/cm
Fig 6.16 Graph of Temp T o k V/s Log K
6.7 Conclusions:
1. Gel growth technique is suitable for growing crystals of Bismuth-
Trisulphide.
2. Different habits of Bismuth trisulphide crystals can be obtained by
changing parameters like gel density, gel aging, pH of gel, Concentration
of reactants etc.
3. Well known Liesegang phenomenon is observed in the growth of
Bismuth-Trisulphide crystals.
4. Unit cell parameter values nearly match with the reported ones and the
structure of Bismuth-Trisulphide is Rhombus or Orthorhombic,
confirmed by XRD.
5. Fundamental infrared frequencies observed in all Sulphide compounds
in general, are also found in the present FT-IR analysis, of Bismuth-
Trisulphide.
0
0.5
1
1.5
2
2.5
3
305 313 323 333 343 353 363 373 383 393 403 413 423
Series 1
275
6. Chemical compositions of the grown crystal by volumetric Analysis, and
gravimetric Analysis well match with the theoretical calculation from
molecular formula.
7. Crystals are quite transparent, and are of good quality.
8. Magnetic measurement is importance in solving problems of molecular
structure and bond type of the material. Offers, a means of detecting the
presence of singly occupied electronic orbit. The value of magnetic
susceptibility of Bi2S3 closely related to theoretical ones. i.e. material Bi2S3 is
diamagnetic up to 1K Gauss and behaves as a paramagnetic substance
above 1K Gauss. Magnetic susceptibility is decreased as increase in
temperature.
9. The electrical conductivity of crystals closely related to theoretical values
with chemical nature of compound the electrical conductivity increases as
increase in temperature. The energy gap of Bi2S3 is found to be 0.4640 eV
which suggest that sample is semiconductor.
10. Chemical analysis confirms the presence of Bismuth and Sulpher, Chemical
compositions of the grown crystal by EDAX match with the theoretical
calculation from molecular formula.
11. Circular shape of Bismuth Tri-Sulphide crystals of appreciable size can be
grown by single diffusion gel technique.
12. From SEM the grain size of sample is pentagonal and triangular.
13. Water of crystallization is present in grown crystals confirmed by TGA, DTA and
FT-IR analysis.
276
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